1. Field of the Invention
The present invention relates to a device intended to measure, on the one hand, the angle of freedom of two adjacent vertebrae in torsion and, on the other hand, the angle of freedom of these vertebrae in lateral inflexion with respect to a given position in flexion-extension of the vertebrae.
2. History of the Related Art
In theory, it is considered that the intervertebral articulation comprises 6.degree. of freedom, but, in practice, the principal freedom of the articulation lies in flexion-extension. Similarly, but to a lesser amplitude, there exist degrees of freedom upon intervertebral horizontal rotation or lateral flexion.
It should also be noted that these two movements are usually linked with each other, i.e. the lateral flexion necessarily causes a certain horizontal degree of rotation, and vice versa.
The problem of this lumbar intervertebral articulation is that it is rapidly subject to damage, leading to a reduction in the rubbery quality of the disc. Such deterioration results in a greater suppleness of the articulation, which brings about more ample movements both in flexion-extension, but also in lateral inflexion and in torsion.
The reduction in the rubbery quality of the disc leads to a complete disorganization of the movements of the lumbar intervertebral articulation.
It therefore seems important, for certain therapeutical decisions, both to be able to measure the amplitude of all the intervertebral movements and to have an idea of the disorganization of the coupling of the movements with respect to one another.
It is a particular object of the present invention to provide a solution to this problem.